1. Field of the Invention
The present invention relates to a cassette for accommodating a tape-shaped material having an electrically conductive layer such as an electrophotographic film in which the tape-shaped material wound on a reel is accommodated in a cassette casing.
2. Description of the Related Art
Projecting and/or recording systems, which enable an image to be recorded on a predetermined frame of such a photosensitive film as the electrophotographic film and which also permit the recorded image to be projected or copied, have already been proposed in, e.g., U.S. Pat. Nos. 3,697,176 and 3,972,610 and U.S. patent application Ser. Nos. 632,222 now U.S. Pat. No. 4,619,519 and 920,336 filed Oct. 17, 1986 now U.S. Pat. No. 4,727,393.
For the purpose of keeping and handling the film applied to the apparatuses proposed in the above patents and applications, it is convenient to accommodate it in a cassette casing. However, when an image is recorded on a film having an electrically conductive layer, for example, an electrophotographic film, the electrically conductive layer must be grounded to release electric charge accommodated on an exposed portion of the film. Accordingly, a system where a reel on which the film is wound and a driving shaft driving the reel are electrically connected to each other is disclosed in U.S. Pat. No. 4,572,649. Also, a system where a leaf spring retaining the reel serves as a contact piece is disclosed in U.S. patent application Ser. No. 819,077 now U.S. Pat. No. 4,685,638. The grounding construction disclosed in the U.S. patent application Ser. No. 819,077 is as follows: The contact piece is secured to one end face of a take-up reel for winding the film to provide electrical connection between the contact piece and the electrically conductive layer, and a reel retainer which contacts the contact piece is secured to a cassette casing accommodating the electrophotographic film, the reel retainer being grounded.
When the film is advanced, the reel is rotated, and the contact piece is also rotated while being in contact with the reel retainer.
The following undesirable conditions can arise due to the conditions of use of the cassette.
During this rotation of the reel, heat is generated due to the friction occurring between the contact piece and the reel retainer, causing oxide film to be formed on the surfaces of the contact portions. In addition, dust is generated due to the wear of the contact piece and the reel retainer. Such oxide film and dust cause a contact failure and hence incomplete grounding, resulting in a problem such as fogging of the recorded image.
Further, the dust may be scattered to adhere to the electrophotographic film, so that the film may be flawed and images recorded thereon may be damaged by the dust during the repetition of winding and rewinding of the film.